Coating aid for gelatin and gelatinous silver halide emulsions



United States This invention relates to gelatin compositions containing as coating aids therein amide and ester derivatives of sulfoacetic acid salts.

In the application of gelatin coatings to surfaces, particularly in the photographic industry, it is desirable to apply layers of gelatin compositions to surfaces, uniformly and at good product speeds. In many cases it is desirable to apply gelatin coatings over previous layers, either of gelatin or of some other material, the pre vious layers being either wet or dry.

In the coating of film or paper with a gelatin layer, such as of a photographic emulsion or some other gelatin composition, evenness of coating is desirable. When no coating aid is used, coating defects are evident, for example, the final product may show numerous crescentshaped uncoated areas, i.e. repellency spots, about the size of a pin head with streaks running from the points of the crescent .in a direction opposite to that of the coating. Often lightly coated areas of 5-10 mm. in diameter will appear.

. Wheni saponin, the conventional coating aid, is'used in gelatin coating compositions, the layer obtained when dried is .ordinarily a uniformly even coating, which can be rewet readily. .Saponin, however, may vary markedly from batch to batch both in quality and composition. This mayadversely affect a photographic emulsion containing-it or it may result in little or no improve ment in coating properties in the composition to which it is added.

A number of synthetic materials have been suggested as coating aids in gelatin compositions, but often these synthetic materials are deficient in one respect or another. For instance, a synthetic. coating aid which may overcome repellency satisfactorily and produce uniform coatings of photographic paper emulsions by a hopper technique, may result in surfaces that cannot be rewet readily, so that the producttends to form air bells on the emulsion surface during processing incommencial processing machines. 'Ihese difiicult-to-rewet areas Where the air bells form will manifest themselves as small undeveloped areas in the processed product. To overcome this disadvantage, saponin has been employed as an-additive to the emulsion, but due to the desirability of finding substitutes for saponin, other materials are believed to be more useful in this connection. A

' In the manufacture of photographic film and paper, coating techniques have been developed which allow the simultaneous application of two or more gelatin layers to film base or paper. Some of the previously suggested synthetic coating aids and the conventional saponin do not yield satisfactory coatings when the multiple coating technique is applied. Defects such as pencil line streaks, mottle and general streakiness frequently characterize the coatings obtained with saponin as the coating aid in multiple hopper coating operations.

This invention has for an object to provide an improved coating aid for applying aqueous gelatin coatings to either wet or dry surfaces. Another object of our invention is to provide a coating aid for use inphotosenatent O Patented Dec. 11, 1962 sitive gelatin emulsions to facilitate the obtaining of coatings which are uniformly even and repellency-free without adversely affecting the emulsion. A further object of our invention is to supply coating aids which will result in gelatin layers which can be rewe't readily but which are not significantly altered in surface roughness. A still further object of our invention is to provide compositions of gelatin and certain synthetic chemical compounds having valuable characteristics as photographic layers. A still further object is to supply coating aids which allow the satisfactory simultaneous application to photographic film base and paper of two or more gelatin layers. Other objects of our invention will appear herein.

We have found that certain derivatives of sulfoacetic acid salts are of value in gelatin compositions as coating aids and that these compounds will endow the dried surface of the gelatin coatings with susceptibility to reaids have been found to impart valuable characteristics to gelatin compositions when incorporated therein in very small quantities such as in amounts of 0.1% based on the Weight of the gelatin. Larger quantities of these compounds, however, can be used in gelatin compositions to impart good properties such as in proportion of from 0.4% to 1.5% or even up to 3% based on the weight of the gelatin. The compounds which we have found to be useful as coating aids are amide and ester derivatives of sulfo acetic acid salts having the formula:

RA--XCH SO M where R is an alkyl, alicyclic, alkaryl or acyl group; A is (0CH CH n being an integer from O to 10;: X is --NHC(:O)- or OC(:O); and M is an alkali metal or ammonium ion. Representative alkyl groups include straight or branched chains of 8 to 18. carbon atoms, such as octyl, lauryl, tridecyl, tetradecyl, stearyl, and the like. Alicyclic groups are illustrated by the abietyl species. Alkaryl groups may be represented by a phenyl ring with alkyl substituents of straight or branched chains containing 5 to 12 carbon atoms. Representative acyl groups are those derived from a1- kanoic acids, such as lauroyl (from lau ric acid), and from alkyl-substituted aromatic acids, such as p-(tert-octyl) benzoyl (from p-(tert-octyl) benzoic acid).

One of the preferred species representative of an amide derivative of sulfoacetic acid salt is the potassium saltof the lauric acid ester of the ethanolamide of sulfo-.

acetic acid (H):

This surfactant is available commercially and is sold under the designation Sulfocolaurate by the Emulsol Chemical Corporation.

The ester derivatives of sulfoacetic acid are prepared by a conventional reaction of the corresponding alcohol and sulfoacetic acid in a medium such as benzene with continuous removal of the azeotroped Water. The resulting sulfoacetate ester is converted to the desired sulfonate salt by treatment with alkali or ammonia. The alcohols may be simple alcohols or they may be polyethylene oxide derivatives of a simple alcohol. The abietyl derivatives, for example, are obtained by treating with ethylene oxide a commercially available alcohol, Abitol from.

HerculesPowder Company, comprising about 38.2%

CH; CHgOH about 34% of a)2 on.

about 2.8% of CH: CHaOH and about 15% of non-alcoholic material. Other useful alcohols of related structure are the polyethoxyethanols described on page 202 of A.M. Schwartz and J. W. Perry, "Surface Active Agents, vol. 1, Interscience Publishers, Inc., N. Y. (1949). For example suitable coating aids of the sulfoacetate ester type may be prepared by the following procedure:

(A) A mixture of 70 g. of tridecoxydiethoxyethyl alcohol and 29.3 g. of sulfoacetic acid in 100 ml. of benzene is refluxed with rapid stirring for three hours, the azeotroped water being collected in a Dean-Stark trap. The solvent is removed under vacuum at about 60 C. The resulting material is diluted with 150 ml. of water and neutralized by the gradual addition of 8.4 g. of sodium hydroxide in percent aqueous solution while maintaining the temperature at 20. The solution is diluted with water and filtered through a bed of Super Cel (a diatomaceous filter aid). The resulting solution of sodium tridecoxydiethoxyethyl sulfoacetate contains 6.5 percent total solids, as determined by taking a weighed sample to dryness.

(B) Sodium abietoxyoctaethoxyethyl sulfoacetate is prepared from 100 g. of abietoxyoctaethoxyethyl alcohol and 19.6 g. of sulfoacetic acid in the manner described in A.

(C) Sodium p-(tert-octyl)phenoxytetraethoxyethyl sulfoacetate is prepared from 74.7 g. of p-(tert-octyl)phenoxytetraethoxyethyl alcohol and 24.6 g. of sulfoacetic acid in the manner described in A.

Our invention relates to coating a support with a gelatin coating composition, either as an aqueous solution of gelatin or as a photographic emulsion which ordinarily is composed of an equeous solution of gelatin containing as the light sensitive material therein, a silver halide such as silver bromide, silver chloride, silver iodide, or their mixture. The emulsion may contain other added materials such as sensitizing dyes, hardeners, or the like. Descriptions of photographic emulsions are found in various places in the prior art such as in Fundamentals of Photographic Theory by James and Higgins; John Wiley and Sons, 1948, Chapter 2.

The coating procedure outlined may comprise any of the standard procedures employed in the industry. As an instance'of such procedure, paper base to be coated is passed through a trough or other reservoir whereby a coating is applied to the paper base. The coating is applied in greater thickness than desired and the surface is then subjected to the action of some leveling means such as a doctor blade or an air brush which causes run back of the coating composition and results in an even surface. In some cases it may be desirable to apply several coatings simultaneously in the manner described in U.S. Patent No. 2,761,791 of TA. Russell or in the coating operations described in U.S. Patents 2,761,417, 2,761,418 and 2,761,419. In some cases the coating method may involve a hopper technique in which the thickness of the layer is regulated by the rate at which the coating composition is deposited upon the base which is moved along adjacent thereto. The following examples illustrate coating procedures employing compositions in accordance with our invention:

EXAMPLE 1 In the simultaneous application of two gelatin layers consisting of gelatin-silver halide photographic emulsions containing 7% of gelatin by means of a hopper technique, the following results are obtained when sodium tridecoxydiethoxyethyl sulfoacetate (I) is used as the coating aid. In this experiment the coverages for the upper and lower layers are 1.5 and-0.5 lbs. of wet coating melt per ft.

Surfactant Concentration in g./ lb. of Wei Coating Mel t Surfactant Lower Upper Repel- Layer Layer Iencies 0. 0 0. 0 Few 0. 0 0. 13 0 0. 0 0.25 O 0. 0 0. 5 0 0. 07 0. 13 0 0. 07 0. 25 (I 0. 07 0. 5 0 0. 13 0. 25 0 0. 13 0. 5 0 0. 25 0. 25 0 O. 25 0. 5 0

EXAMPLE 2 In a single layer coating of a gelatine-silver halide photographic emulsion, the use of Sulfocolaurate" (II) results in satisfactory coatings which, although too slippery for certain products, are characterized by superior developer wetting properties.

In a single layer coating similar to that described in Example 2, the use of sodium p-(tert-octyl) phenoxytetraethoxyethyl sulfoacetate (III) results in satisfactory coatings, less slipper than those obtained with Sulfocolaurate, as the coating aid and characterized by satisfactory developer wetting properties.

Gone. in Coeff. of Developer Surfactant 1;.llb. of friction spreading emulsion C mtrol 0.0 0.517 2. 83 Sa'nnim Standard 0. 4M 6. 6) III- 0. 25 0. 332 6. 6') III- 0. 50 O. 320 6. 16

5 EXAMPLE 4- v In a single layer coating similar to that described in Example 2 the use of sodium abietoxyoctaethoxyethyl s'ulfoacetate (IV) as the coating aid results in satisfactory coatings, less slippery than those obtained with sulfoco laurate, and characterized by superior developer wetting properties. V

acetate (1) as the coating aid results in satisfactory coatings less slippery than those obtained with Sulfocolaurate as the coating aid and characterized by superior developer wettingproperties.

Gone. in Coefi. of Developer Surfactant g., 1b. of friction spreading emulsion I 0.0 L485 4.15 Standard 0.507 6.60 0.25 0. 298 7. 07 0.5 0.276 8.55

' EXAMPLE 6 Coatings were applied to film base by a hopper technique giving the following results with the sodium salts of p- (tert-octyl)phenoxytetraethoxyethylsulfoacetate (III), abietoxyoctaethoxyethyl sulfoacetate (IV) and tridecoxydiethoxyethyl sulfoacetate (I).

I Surf. Repell; Long.

Surfactant cone, in 25 ft. Mottle streaks 0.0 19 Medium; Slight-l 0. 22 0 Slight-F--- Medium. 0.22 0 ,.';do Do.

0.22 0 Slight"--. Slight.

, In the use of the gelatin coating compositions in accordance with our invention if a film base is to be coated, it may be composed of any of the usual conventional film base materials. This may be a sheet of cellulose nitrate or of an organic acid ester of cellulose. It is often desirable first to apply a subbing layer to the cellulose ester base to facilitate adhesion of the photographic emulsion thereto, this practice of subbing being well known in the art. As for photographic paper, a description thereof is found in Kodak Data' Book, 5th edition, Kodak Papers, pages 3 and 4. A base material of the type described there would preferably be employed for preparing photographic paper in accordance with the present invention.

' Not only are the coating aids of our invention and their mixtures with other coating aids useful in gelatin over; coating compositions, but they are also useful in various other types of coating compositions in which gelatin is an important constituent. For instance, these coating aids are useful in gelatin photographic emulsions, not only those which are nonoptically sensitized, but also in orthochromatic, panchromatic and X-ray emulsions, either before or after the addition of any sensitizing dyes or sensitizer or other addenda. This also includes gelatin emulsions intended for color photography such as those containing color forming couplers. Coating aids in accordance'w'ith'our invention are also useful in gelatin coating '6 compositions to be applied, for example, as antihalation layers, antistatic layers, filter layers, or in any type, of gelatin layer which is coated from a composition consisting essentially of an aqueous solution of gelatin.

The emulsions can be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds can be added such as those described in Sheppard U.S. Patent 1,574,944, issued March 2, 1926, Sheppard et a1. U.S. Patent 1,623,499, issued April 5, 1927, and Sheppard et al. U.S. Patent 2,410,689, issued November 5, 1946. v

The emulsions can also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium, and platinum. Representative compounds are ammonium chloropalladate, potassium chloroplatinate, and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U.S. Patent 2,448,060, issued August 31, 1948, and as antifoggants in higher amounts, as described in Trivelli and Smith U.S. Patents 2,566,245, issued August 28, 1951, and 2,566,263, issued August 28, 1951.

The emulsions can also 'be chemically sensitized with gold salts as described in Waller et a1. U.S. Patent 2,399,- 083, issued April 23, 1946, and Damschroder et a1. U.S. Patent 2,642,361, issued June 16, 1953. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-. aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agents such as stannous salts (Carroll U.S. Pat.- ent 2,487,850,:issued November 15, 1959), polyamines, such as diethyl triamine (Lowe and Jones U.S. Patent 2,518,698, issued August 15, 1950), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925, issued September 12, 1950), or bis-(fl-aminoethyl) sulfide and its water-soluble salts (Lowe and Jones U.S. Patent 2,521,-. 926, issued September 12, 1950) r The emulsions can also be optically sensitized with cyanine and merocyanine dyes, such as those described in Brooker U.S. Patents 1,846,301, issued February 23, 1932; 1,846,302, issued February 23, 1932; and 1,942,854, issued January 9, 1934; White U.S. Patent 1,990,507, issued February 12, 1935; Brooker and White U.S. Patents 2,112,140, issued March 22,1938; 2,165,338, issued July 11, 1939; 2,493,747, issued January 10, 1950, and 2,739,- 964, issued March 27, 1956; Brooker and Keyes U.S. Patent 2,493,748, issued January 10, 1950; SpragueU.S. Patents 2,503,776, issued April 11, 1950, and 2,519,001, issued August 15, 1950; Heseltine and Brooker U.S. Patent 2,666,761, issued January 19, 1954; Heseltine U.S. Patent 2,734,900, issued February 14, 1956; ,VanLare. U.S. Patent 2,739,149, issued March 20, 1956; and Kodak Limited British Patent 450,958, accepted July 15, 193.6. The emulsions can also be stabilized with the mercury compounds of Allen, Byers and Murray U.S. Patent 2,728,663, issued December 27, 1955 Carroll and Murray U.S. Patent 2,728,664, issued December 27, 1955; and Leubner and Murray U.S. Patent 2,728,665, issued December 27, 1955; or with gold salts as described in Damschroder U.S. Patent 2,597,856, issued May 27, 1952, and Yutzy and Leermakers U.S. Patent 2,597,915, issued May 27, 1952; the triazoles of Heimbach and Kelly U.S. Patent 2,444,608, issued July 6, 1948; the azaindenes-of Heimbach and Kelly U.S. Patents 2,444,605, and 2,444, 606, issued-July 6, 1948; Heimbach U.S. Patents 2,444,; 607, issued July 6, 1948, and 2,450,397, issued September 28, 1948; Heimbach and Clark U.S. Patent 2,444,609, issued July 6, 1948; Allen and Reynolds U.S. Patents 2,713,541, issued July 19, 1955, and 2,743,181, issued April 24, 1956; Carroll and Beach U.S. Patent 2,716,062, issued August 23, 1955; Allen and Beilfuss U.S. Patent 2,735,769, issued February 21, 1956; Reynoldsand Sagal U.S. Patent 2,756,147, issued July 24, 1956; Allen and' and those disclosed by Birr in Z. wis's. Photf', vol. 47, 1952, pages 2-28; the disulfides of Kodak Belgian Patent 569,317, iss'ued July 31, 1958; the quaternary benaothiazolium compounds of Brooker and Stand U.S. Patent 2,131,038, issued September 27, 1938, or the polymethylene bis-henzothiazolium salts of Allen and Wilson U.S. Patent 2,694,716, isued November 16, 1954; the zinc and cadmium salts of Jones U.S. Patent 2,839,405, issued June 17, 1958; and the carboxymethylmercapto compounds of Murray, Reynolds and Van Allen U.S. Patent 2,819,965, issued January 14, 1958.

The emulsions may also contain speed-increasing compounds of the quaternary ammonium type of Carroll U.S. Patent 2,271,623, issued February 3, 1942; Carroll and Allen U.S. Patent 2,288,226, issued June 30, 1942; and Carroll and Spence U.S. Patent 2,334,864, issued November 23, 1943; or the polyethylene glycol type of Carroll and Beach U.S. Patent 2,708,162, issued May 10, 1955; or the quaternary ammonium salts and polyethylene glycols of Piper U.S. Patent 2,886,437, issued May 12, 1959;

aswell as the thiopolymers of Graham and Sagal U.S. patent application Serial No. 779,839, filedDecember 12, 1958, and the' Dannand Chechak US: applicationSerial No; 779,874, filed December 12,1958;

The emulsions may contain a suitable gelatin'plasticizer such as glycerin; a dihydroxy alkane such as 1,5-pentane diol as'described in Milton and Murray U.S. application Serial No. 588,951, filed June 4, 1956; an ester of an ethylene bisglycolic acidsuch as ethylene bis(methyl glycolate) as described in Milto'nU;S. application Serial No, 662,564, filed May 31,1957; bis(etlioxy diethylene glycol) succinate as describedin Gray UlS. application Serial No. 604,333, filed August 16, 1956, ora polymeric hydrosol as results from the emulsion polymerization of a mixture of an amide of an acid of the acrylic acid series, an acrylic acid'ester and a styrene-type compound as de= scribed in Tong U.S. Patent 2,852,386, issued September 16, 1958. The plasticizer may be added to the emulsion beforeor after the'addition of a sensitizing dye, if used.

The emulsions may be hardened wtih any suitable hardener for gelatin such as formaldehyde; a halogen-substituted aliphatic'acid such as mucobromic acid as described in White U.S. Patent 2,080,019, issued May 11, 1937; a compound having a plurality of acid anhydride groups such as 7,8'diphenylbicyclo (2,2,2)-7-octene-2,3,5,6-tetracarboxylic dia-nhydride, or a dicarboxylic or a disulfonic acid chloride suchas terephthaloyl chloride as described in Allen and Carroll U.S. Patents 2,725,294, and 2,725, 295, both issued-November 29, 1955; a cyclic 1,2 diketo'ne such as cyclopentane-1,2-dione as described in Allenand Byers U.S. Patent"2,725,305, issued November 29, 1955; a biester of methane-sulfonic acid such as 1,2-di-(methanesulfonoxy)-ethane as described in 'Allen and Laakso U.S. Patent 2,726,162, issued December 6,1955;- 1,3-dihydrox'ymethylbenzimidazol-Z-one as described in July, Knott and Pollak U.S.' Patent 2,732',3l6,- issued January 24, 1956; a dialdehyde ora sodium bisulfite derivative thereof such as B-methyl glutarald'ehyde bis-sodium bisulfite as described in Allen and Burness U.S. patent application Serial No. 556,031, filed December 29, 1955; a bisaziridine carboxarnide such astrimethylene bis( l-aziridine carboxamide) as described in Allen and Webster U.S. patent application Serial No'. 599,891, filed July 25, 1956; 2,3-dihydroxy dioxane as described in Jefireys U.S. Patent 2,870,013, issued'January 20, 1959;or bisisocyanate as described in Henn et al. U.S. patent application Serial No. 805,357, filed April 10, 1959.

The addenda which we have described may be used in various kinds of photographic emulsions. In addition to being useful in X-ray and other nonoptically sensitized emulsions they may also'be used in orthochromatic, panchromatic and infrared sensitive emulsions. Theymay be added to the emulsion before or after'any sensitizing dyes which are used. Various silver salts may be used asnthe sensitive: salt such as. silver bromide, silver iodide,

silver chloride, or mixed silver halides such as silver chlorobromide orsilverbromoiodide. The agents may be used in emulsions intended for color photography, for example, emulsions containing color-forming couplers or emulsions to be developed by solutions containng couplers or other color-generating materials, emulsions of the mixed-packet type, such as described in Godowsky U.S. Patent 2,698,- 794, issued January 4, 1955; or emulsions of the mixedgrain type, such as described in Carroll and Hanson U.S. Patent 2,592,243, issued April 8, 1952. These agents can also be used in emulsions which form latent images predominantly on the surface of the silver halide crystal or in emulsions which form latent images predominantly inside the silver halide crystal, such as those described in Davey and Knott U.S. Patent 2,592,250, issued April 8, 1952.

These may also be used in" emulsions intended for use in diffusion transfer processes which utilize the undeveloped silver halide in the nonimage areas'of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a receiving layer in close proximity to the original silver halide emulsion layer. Such processes aredescribed'in Rott'U;S. Patent 2,352,- 014, issued June 20, 1944, and Land U.S. Patents 2,584,- 029, issued January 29, 1952; 2,698,236, issued December; 28,1954, and 2,543,181, issued February 27 1951; and Ya'ckel et a1. U.S. patent application Serial No. 586,705, filed May- 23,- 1956. j They may also be used in color transfer processes which utilize the diffusion transfer of an image-wise distribution of developer, coupler or dye, from alight-sensitive layer'to a second layer, while the two layers are in close proximity to one another. Color processes of this type are described in Land U.S. Patents 2,559,643, issuedJuly 10, 1951, and 2,698,798, issued January 4, 1955; Land and Rogers Belgian Patents 554,933 and 554,934, granted August 12, 1957; International Polaroid Belgian Patents 554,212, granted July 16, 1957, and 554,935, granted August 12, 1957; Yutzy U.S. Patent 2,756,142, granted July 24, 1956, and Whitmore and Mader U.S. patent application Serial No. 734,141, filed May 9, 1958. They may also be used in emulsions intended for use in a monobath process such as described in Haist et a1. U.S. Patent 2,875,048, issued February 24, 1959, and in web-type processes, such as the one described in Tregillus et al. U.S. patent application Serial No. 835,473, filed August 24, 1959.

In the preparation of the silver halide dispersions employed for preparing silver halide emulsions, there may be employed as the dispersing agent for the silver halide in its preparation, gelatin or some other colloidal material such as colloidal albumin, a cellulose derivative, or a synthetic resin, for instance, a polyvinyl compound. Some colloids which may be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in Lowe U.S. Patent 2,286,215, issued June 26, 1942; a far by drolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 19-26% as described in U.S. Patent 2,327,808, of Lowe and Clark, issued August 24, 1943; a water-soluble ethanolamine cellulose acetate as described in Yutzy U.S. Patent 2,322,085, issued June 15, 1943; a polyacrylamide or an imidized polyacrylamide as described in Lowe, Minsk and Kenyon U.S. Patent 2,541,474, issued February 13, 1951; zein as described in Lowe U.S. Patent 2,563,701, issued August 7, 1951; avinyl alcohol polymer containing urethane carboxylic acid groups of the type described in Unruh and Smith U.S. Patent 2,768,154, issued October 23, 1956; or containing cyano-acetyl groups such as the vinyl alcohol-vinyl cyanoacetate copolymer as described in Unruh, Smith and Priest U.S. Patent 2,808,331, issued October 1, 1957; or'a polymeric material which results from polymerizing-a protein or a saturated acylated pro- 'tein' with a monomer having a vinyl group as described in U.S. Patent 2,852,382, of Illingsworth, Dann and Gates, issued September 16, 1958;

If desired, compatible mixtures of two or more of these colloids may be employed for dispersing the silver halide in its preparation. Combinations of these antifoggants, sensitizers, hardeners, etc., may be used.

We claim:

1. An aqueous gelatin coating composition comprising an aqueous solution of gelatin of 1 /z-14% concentration containing therein a small amount of a coating aid having a chemical composition represented by the following formula:

R--( OCH CH X R being selected from the group consisting of alkyl, alicyclic, alkaryl and acyl radicals of at least 8 carbon atoms; 11 being an integer from 1-10; X being a radical selected from the group consisting of:

--NH(H3CH2SO3M and M being a substituent selected from the group consisting of alkali metal, ammonium and substituted ammonium.

2. A gelatin-silver halide photographic emulsion which contains a small amount of a coating aid having a chemical composition represented by the following:

R(OCH CH X R being selected from the group consisting of alkyl, alicyclic, alkaryl and acyl radicals of at least 8 carbon atoms; n being an integer from 1-10; X being a radical selected from the group consisting:

10 the coating aid therein a small amount of an alkali metal salt of the lauric acid ester of the ethanolamide of sulfoacetic acid.

4. A gelatin-silver halide photographic emulsion containing a small amount of an alkali metal salt of the lauric acid ester of the ethanolamide of sulfoacetic acid.

5. An aqueous gelatin coating composition comprising an aqueous solution of gelatin of 1 /z-l4% concentration and as the coating aid therein a small amount of sodium tridecoxydiethoxyethyl sulfoacetate.

6. A gelatin-silver halide photographic emulsion con taining a small amount of sodium tridecoxydiethoxyethyl sulfoacetate.

7. An aqueous gelatin coating composition comprising an aqueous solution of gelatin of 1 /214% concentration and as the coating aid therein a small amount of sodium p (tert-octyl)phenoxytetraethoxyethyl sulfoacetate.

8. A gelatin-silver halide photographic emulsion containing a small amount of sodium p-(tert-octyl)phenoxytetraethoxyethyl sulfoacetate.

9. An aqueous gelatin coating composition comprising an aqueous solution of gelatin of 1 /2-14% concentration containing as a coating aid therein a small amount of sodium abietoxyoctaethoxyethyl sulfoacetate.

10. A gelatin-silver halide photographic emulsion containing a small amount of sodium abietoxyoctaethoxyethyl sulfoacetate.

References titted in the file of this patent UNITED STATES PATENTS 2,240,470 Swan Apr. 29, 1941 2,400,532 Blake et a1. May 21, 1946 2,719,087 Knox et al Sept. 27, 1955 FOREIGN PATENTS 808,228 Great Britain Ian. 28, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 3 O68 lO1 December ll 1962 William J Knox Jr et alo It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 9 lines 17 to 19 and lines 32 to 34 the formulas each occurrence should appear as shown below instead of as in the patent:

Signed and sealed this 15th day of October I963 (SEAL) Attest:

EDWIN L0 REYNOLDS ERNEST W. SWIDER Attesting Officer Ac ting Commissioner of Patents 

1. AN AQUEOUS GELATIN COATING COMPOSITION COMPRISING AN AQUEOUS SOLUTION OF GELATIN OF 11/2-14% CONCENTRATION CONTAINING THEREIN A SMALL AMOUNT OF A COATING AID HAVING A CHEMICAL COMPOSITION REPRESENTED BY THE FOLLOWING FORMULA: 